This invention relates to tissue-retrieving means for a surgical open-snare instrument, and, more particularly, to such means and instrument suitable for removing projecting body tissue.
Snare instruments are employed for removing projecting normal and abnormal body tissue, in particular, tonsils and nasal polyps. Such instruments utilize a wire snare, which is lopped around the tissue to be removed, and then is contracted to sever the tissue from the body as the loop is reduced in size.
A surgical snare instrument typically comprises a barrel, and a resilient snare loop-forming wire carried by the barrel. The instrument is handheld and has mechanism enabling a surgeon to extend the wire beyond the distal end of the barrel, where it is expanded to form a loop for encircling projecting body tissue. The wire then may be retracted into the barrel, thereby contracting the loop, which cuts through the encircled body tissue as it contracts.
Two types of surgical snare instruments have been used: those having a "covered" snare, and those having an "open" snare. Covered-snare instruments have an annular structure at the distal end of the barrel, which receives and shapes the snare loop. Both the loop and the receiving structure encircle the body tissue, and the tissue is severed by contracting the loop. Open-snare instruments have no loop-receiving structure, but the snare loop is freely formed and contracted at the distal end of the barrel. An open-snare instrument is preferred for use in removing nasal polyps, to minimize bulk and obstruction of the field of view, and permit the loop to be adjusted freely, according to the situation. The present invention is concerned with open-snare instruments.
When nasal polyp or tonsil tissue is severed from the body by means of a snare instrument, it is necessary to retrieve or recover the severed tissue, avoiding inhalation or swallowing of the tissue in the process. Most frequently, polyps and tonsils are removed by an aspiration or suction device, operated by an assistant to the surgeon using the snare instrument. Previously, various tonsilotomes have been proposed that incorporate a harpoon-like tissue-retriever, on which the tissue is impaled, for removal after being severed from the body. However, we are not aware that such prior tonsilotomes are being sold now, or that the same or similar instruments are being sold for other purposes, particularly for use as nasal snares, or that any open-snare instrument has been provided with any kind of tissue-retrieving means.
Nasal polypectomies pose unique problems. Usually, they are carried out with the patient in a reclining position, and, often, under only local anesthesia. The windpipe of a patient under local anesthesia is not shielded by the endotracheal tube commonly employed when general anesthesia is used. Hence, when a polypectomy is performed under local anesthesia, precautions must be taken to prevent the severed polyp from falling through the nasal passages of the patient into the nasopharynx, where it may be inhaled and block the patient's airway. If an inhaled polyp is not coughed up by the patient, major medical procedures may be necessary to remove it.
In polypectomies, the snare loop typically is positioned to sever the portion of the polyp--the "stalk"--connecting the body of the polyp to the wall of the nostril. To minimize the risk of having the severed polyp fall back into the nasal passage, and to make it easier for an assistant to aspirate it, the surgeon often will not cleanly sever the polyp by completely contracting the loop about the encircled polyp stalk. Instead, the surgeon will partially contract the loop, thereby partially cutting through the stalk, then will complete the removal of the polyp by avulsion: by pulling the wire through the remainder of the stalk, thereby tearing away the polyp while tending to pull it forward out of the nostril. However, avulsion of a polyp tends to produce greater tissue damage, bleeding, and patient discomfort, then does clean severing thereof.